Techno-economic assessment of Carnot batteries for load-shifting of solar PV production of an office building

Abstract

This study presents a techno-economic assessment of Carnot batteries for load-shifting of solar PV production of an office building considering variable electricity production, demand and pricing. The building has an annual electricity demand of 2600 MWh and a maximum power demand of 0.564 MW. The Carnot battery studied is based on a subcritical Rankine cycle with sensible thermal storage. A generic Carnot battery model and sizing methodology are presented and applied to the case study. It is found that implementing a Carnot battery is not cost effective for the studied case. Larger system sizes increase the integration of solar PV production, but decrease the net present value. Increasing the thermodynamic efficiency of the Carnot battery is beneficial to improve the financial feasibility and to reach higher levels of solar PV integration. The system investment cost should reduce minimally with a factor 9.4 and 4.1 to make the base and ideal system viable respectively. Alternatively, a minimum electricity tax or 326 €/MWh and 122 €/MWh could be implemented. The Carnot battery is not financially competitive with Li-ion batteries under the current scenario. The ideal Carnot battery becomes competitive at charging durations starting from 7 h.